Analysis of Differences of Opinion Over BPL Interference Issues Ed Hare, W1RFI ARRL Laboratory Manag

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Analysis of Differences of Opinion Over BPL
Interference IssuesEd Hare, W1RFIARRL
Laboratory Manager225 Main StNewington,CT
06111w1rfi_at_arrl.org860-594-0318
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What Are Our Differences?

• Interference is very rare vs interference will be
  everywhere
• BPL signals are very weak vs BPL signals are very
  strong
• BPL signals will be strong along miles of power
  line vs BPL signals are point sources that will
  be audible for only a short distance near the BPL
  device
• Mobile stations can just drive away from BPL
  interference vs mobile stations will experience
  BPL over large areas
• BPL is no different than other noises vs BPL is
  the worst noise we have ever heard
• Where do these differences come from?

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Possible Explanations

• The other side is lying to protect its own
  interests and cant be trusted!
• I dont believe it for a minute!
• However, all of our beliefs are shaped by our
  interests
• BPL manufacturers want an environment where they
  can manufacture and sell product
• Radio operators want an environment where their
  radio systems will not be degraded by external
  factors
• Everyones perceptions are shaped by their
  viewpoint, experiences and what methods they use
  to investigate their environment

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Equipment

• Receivers are very sensitive
• A good communications receiver can have a
  sensitivity of less than 0.1 uV, or 140 dBm
• Antennas are very sensitive
• A halfwave dipole on 3.5 MHz has an antenna
  factor of 21 dB/m
• A 3-element Yagi array on 14 MHz has an antenna
  factor of 15 dB/m
• Even a random piece of wire or inefficient mobile
  whip can have an antenna factor of less than 10
  dB/m
• Receiving stations are designed to hear weak
  signals

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Spectrum Analyzers

• Spectrum analyzers are designed for immunity to
  overload, not sensitivity
• A noise floor of 100 dBm dBW is common
• EMC antennas are designed to have broadband
  performance, not gain
• They can have antenna factors ranging from 10
  dB/m for the most sensitive to gt40 dB/m for
  small loops on low HF
• Test equipment is designed to measure relatively
  high signal levels
• Can we be surprised that those who use receivers
  see different things than those that use test
  equipment?

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14 MHz Along a Length of Road
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14 MHz Along a Length of Road
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Same Data Simulated Spectrum Analyzer
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21 MHz Along A Road
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Over the Air Signals Measured on HF
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So Maybe the Other Side Is NOT Lying About
Interference!

• It has been a matter of an incomplete perspective
• A good solution to any problem does not come from
  incomplete engineering
• Our present status is not finding solutions or
  creating a productive environment

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So, what are we going to do?
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It Is Time to Do the Doing

• Uncertainty has cost us all plenty already
• The FCC rulemaking complicated the issue
• If we can get things back to normal, interference
  can be addressed through normal channels
• Light at end of tunnel
• Initial testing in two systems show promise
• Cooperation is the only way we can find common
  ground
• Cooperation requires well, cooperation

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What is Needed in Standard

• Consensus in Denver Interference must be
  addressed
• No need or authority to redefine rules
• Emissions limits / non-interference
• Cannot set threshold for interference
• Can set level to prevent most interference
• Can develop cooperative programs
• Cable industry excellent example
• ARRL would like to have that kind of cooperation
  with all industry
• Standards are one way to do that
• EMC Society?

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EMC   BPL standards must appropriately address
EMC issues. The IEEE EMC Society should be
directly involved in the EMC aspects of any IEEE
standards affecting the BPL industry. The EMC
components of a standard should include the need
of the BPL industry to have a workable
environment in which to manufacture and market
BPL technology and the need for licensed radio
services to operate in a noise environment that
does not result in harmful interference.
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MORE INFORMATIONEd Hare, W1RFIARRL Laboratory
Manager225 Main StNewington,CT
06111w1rfi_at_arrl.org860-594-0318

• http//www.arrl.org/bpl
• http//www.arrl.org/ehare/bpl/hyperlinks.html